• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.8A
• /
• pp.1218-1226
• /
• 1999

In decoding the turbo codes, the sliding window BCJR algorthm, derived from the BCJR algorithm, permits a continuous decoding of the coded sequence without requiring trellis fermination of the constituent codes and uses reduced memory span. However, the number of computation required is greater than that of BCJR algorithm and no study on the effect of the window length has been reported. In this paper, we propose an eddicient sliding window type scheme which maintains the advantages of the conventional sliding window algorithm, reduces its computational burdens, and improves is BER performance. A guideline is first presented to determine the proper window length and then a computationally efficient sliding window BCJR algorithm is obtained by allowing the window to be forwarded in multi-step. Simulation results show that the proposed scheme outperforms the conventional sliding window BCJR algorithm with reduced complexity. It gains 0.1dB SNR improvements over the conventional method for the constraint length 3 and BER $10^{-4}$

• Journal of Advanced Navigation Technology
• /
• v.26 no.4
• /
• pp.226-234
• /
• 2022

With advances in autonomous vehicles and networked control, there is a growing interest in the consensus control of a multi-agents system to control multi-agents with distributed control beyond the control of a single agent. Since consensus control is a distributed control, it is bound to have delay in a practical system. In addition, it is often difficult to have a very accurate mathematical model for a system. Even though a reinforcement learning (RL) method was developed to deal with these issues, it often experiences slow convergence in the presence of large uncertainties. Thus, we propose a slide RL which combines the sliding mode control with RL to be robust to the uncertainties. The structure of a sliding mode control is introduced to the action in RL while an auxiliary sliding variable is included in the state information. Numerical simulation results show that the slide RL provides comparable performance to the model-based consensus control in the presence of unknown time-varying delay and disturbance while outperforming existing state-of-the-art RL-based consensus algorithms.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.964-965
• /
• 2008

본 논문은 고속 영구자석형 동기전동기의 센서리스 제어에 관한 것이다. 정지상태에서 초기 기동시 부터 고속영역까지 센서리스 알고리즘을 구현하기 위하여 슬라이딩 모드 관측기를 적용하여 회전자의 회전각을 실시간으로 관측하여 벡터제어 알고리즘을 구현하였다. 슬라이딩 모드 관측기의 채트링을 개선하고 넓은 속도 범위에서 안정된 응답을 얻기 위하여 속도에 따른 가변 이득 알고리즘과 관측기의 수렴을 여부를 판별하여 제한된 PWM 주기 내에서 관측기를 반복수행 관측기의 성능을 개선하는 알고리즘을 제안 하였다. 또한 제안된 알고리즘을 실험을 통하여 검증을 하였다. 초기 기동시 및 고속 영역에서 우수한 성능의 센서리스 알고리즘 구현되었을 확인하였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.10
• /
• pp.931-940
• /
• 2017

This paper describes a predictive fault diagnosis algorithm for autonomous vehicles based on a kinematic model that uses a sliding mode observer. To ensure the safety of autonomous vehicles, reliable information about the environment and vehicle dynamic states is required. A predictive algorithm that can interactively diagnose longitudinal environment and vehicle acceleration information is proposed in this paper to evaluate the reliability of sensors. To design the diagnosis algorithm, a longitudinal kinematic model is used based on a sliding mode observer. The reliability of the fault diagnosis algorithm can be ensured because the sliding mode observer utilized can reconstruct the relative acceleration despite faulty signals in the longitudinal environment information. Actual data based performance evaluations are conducted with various fault conditions for a reasonable performance evaluation of the predictive fault diagnosis algorithm presented in this paper. The evaluation results show that the proposed diagnosis algorithm can reasonably diagnose the faults in the longitudinal environment and acceleration information for all fault conditions.

• The Journal of Society for e-Business Studies
• /
• v.23 no.3
• /
• pp.225-237
• /
• 2018

The demand for processing large data streams is growing rapidly as the generation and processing of large volumes of data become more popular. A variety of large data processing technologies are being developed to suit the increasing demand. One of the technologies that researchers have particularly observed is the data stream clustering with sliding windows. Data stream clustering with sliding windows may create a new set of clusters whenever the window moves. Previous data stream clustering techniques with sliding windows exploit the coresets, also known as group features that summarize the data. In this paper, we present some reformable elements of a group-feature based algorithm, and propose our algorithm that modified the clustering algorithm of the original one. We conduct a performance comparison between two algorithms by using different parameter values. Finally, we provide some guideline for the selective use of those algorithms with regard to the parameter values and their impacts on the performance.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.2
• /
• pp.147-155
• /
• 2007

In this study, the performance of the modified sliding mode control proposed in the previous study is evaluated for seismic response control of nonlinear hysteretic structures. Modified sliding mode control(MSMC) utilizes the target derivative of Lyapunov function in order to calculate control force, and its performance was evaluated only lot linear structures in the previous study. However, considering that most structures subject to strong earthquake show nonlinear hysteretic behivior, the results from the previous study have limitations in practical application. The results from numerical analyses of single degree of freedom systems and base isolated system, which were described using Bouc-Wen model, indicate that the proposed MSMC algorithm shows better control performance than the existing sliding mode controller.

• Journal of Navigation and Port Research
• /
• v.47 no.4
• /
• pp.256-270
• /
• 2023

In this study, a sliding mode (SM) controller for dynamic positioning (DP) was specifically designed for a turret connection operation of a ship or an offshore structure in which an arbitrary point on the structure could be controlled as the motion center instead of the center of mass. The SM controller allows control of the arbitrary point and provides capability to manage uncertainties in the dynamics of ships and offshore structures, external forces caused by unknown changing marine environments, and transient performance of DP systems. The Jacobian matrix included in kinematic equations of the controlled object was modified to design the SM controller to control based on an arbitrary point of ships or offshore structures. To ensure robustness of the controller, the Lyapunov stability theory was applied in the design of the SM controller. In general, for robustness in DP control, gain scheduling based on a proportional-derivative (PD) control algorithm is employed. However, finding appropriate gains for gain scheduling complicates the application of DP systems. Therefore, in this study, the SM control algorithm was considered to mitigate the complexity of the DP controller for ships and offshore structures. To validate the proposed SM control algorithm, time-domain simulations were conducted and utilized to evaluate the performance of the control algorithm. The effectiveness of the proposed SM controller was assessed by comparing simulation results with results of a conventional PD control algorithm applied in DP control.

• Journal of Power System Engineering
• /
• v.10 no.4
• /
• pp.172-180
• /
• 2006

본 논문은 Dijkstra 알고리즘에 기초한 최단거리 경로계획을 하며 이 경로를 추적하기 위한 슬라이딩 모드 제어를 제시한다. 슬라이딩 모드 제어기는 동적매개변수 불확실성과 입력외란이 존재 시에도 강인 점근적으로 계획된 경로를 추적하도록 한다. 더불어 작업장 내의 이동로봇의 위치를 USB 카메라에 의해 감지하며, Pin-hole 카메라모델로 하여 카메라에 의해 관측되는 작업장 내의 이륜구동로봇의 위치좌표를 결정하였으며, 이 위치를 정확히 감지하기 위해 Tsai법을 사용하여 카메라 보정한다. 시뮬레이션 결과는 슬라이딩 모드 제어기의 성능을 검증하기 위해 보였다.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.14 no.6
• /
• pp.752-758
• /
• 2004

In this paper, we proposed an adaptivefuzzy sliding control algorithm using gradient descent method to reduce chattering phenomenon which is viewed in variable control system. In design of FLC, fuzzy control rules are obtained from expert's experience and intuition and it is very difficult to obtain them. We proposed an adaptive algorithm which is updated by consequence part parameter of control rules in order to reduce chattering phenomenon and simultaneously to satistfy the sliding mode condition. The proposed algorithm has the characteristics which are viewed in conventional VSC, e.g. insensitivity to a class of disturbance, parameter variations and uncertainties in the sliding mode. To demonstrate its performance, the proposed control algorithm is applied to an inverted pendulum system. The results show that both alleviation of chattering and performance are achieved.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.8 no.5
• /
• pp.21-28
• /
• 1998

This study develops a variable structure controller using the time-varying nonlinear sliding surface instead of the fixed sliding surface, which has been the robustness against parameter variations and extraneous disturbance during the reaching phase. By appling TS fuzzy algorithm to the regulation of the rionlinear sliding surface, the reaching time of the system trajectory is faster than the fixed method. This proposed scheme has better performance than the conventional method in reaching time, parameter variation and extraneous disturbance. To demonstrate its performance, the proposed control algorithm is applied to a rotational inverted pendulum.